


Not On Command

by fuzipenguin



Category: Transformers Generation One
Genre: Established Relationship, Knotting, M/M, Other, Sticky Sexual Interfacing, Taboo, Twincest
Language: English
Status: Completed
Published: 2018-03-20
Updated: 2018-03-20
Packaged: 2019-04-04 23:38:21
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 1,588
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/14031363
Author URL: https://archiveofourown.org/users/fuzipenguin/pseuds/fuzipenguin
Summary: Sunstreaker has a brand spanking new interface mod that Sideswipe really wants to try out again. (Has nothing to do with spanking ;)





	Not On Command

**Author's Note:**

> anon tumblr user prompted:sideswipe/sunstreaker, knotting ;)

                Sideswipe’s always saying _something_ when they’re fragging. Curses, encouragements… whatever it is, it’s usually something filthy and stimulating. Sunstreaker’s favorite however, is his very own name. The more desperate sounding, the better.

                 “Sunny, Sunny, _Sunny_ …” Sideswipe’s currently chanting, in between nibbles on the big energon line at the side of Sunstreaker’s neck. “ _Please_ …”

                “Please, what?” Sunstreaker responds, lower half of his body moving smoothly within the vee of his twin’s thighs.

                Sideswipe’s knees press tighter against Sunstreaker’s hips and his pelvis jerks upright to meet Sunstreaker’s next thrust.

                “… want it… please…” Sideswipe chokes out, sounding a little strangled. Sunstreaker smiles smugly against Sideswipe’s collar fairing. There’s nothing hotter than his brother begging in both voice and frame.

                “… the mod… want it…”

                Sunstreaker comes to a complete stop, spike buried deep inside Sideswipe’s valve. Sideswipe whines and his fingers dig into Sunstreaker’s shoulders as Sunstreaker’s head shoots up.

                “What? Now?!”

                He’d only engaged his new interface modality once since he’d gotten it. It had been… an experience, for sure. His spike throbs in remembrance, but his processor is not so awash in pleasure that he can’t see the downsides to the suggestion.

                “We’re on shift in another joor; it’d be cutting it awfully close,” Sunstreaker warns, hips twitching back into his previous rhythm. Sunstreaker vows that they’re both going to overload, mod or not.

                “It’ll be fine,” Sideswipe insists, looking up at Sunstreaker with overly bright optics.

                “But what if we’re not done in time… what if we’re late and someone comes looking… you know we’re not supposed to…” Sunstreaker frets.

                They’re brothers. Twins, and spark-split at that. Physical closeness comes with the territory, but even platonic sleeping together has warranted stares and whispers. If anyone ever found out they were lovers too?

                At best, they’d be discharged; at worst, court martialed and separated. It was a risk they had taken ever since joining the Autobots. Fortunately, once they had gotten their own quarters, interfacing had become much less risky than when they’d snuck around whatever base they were on, looking for a private spot.

                Sideswipe reaches up and yanks Sunstreaker’s head back down, their lips crashing together. The kiss is deep and dirty, Sideswipe using all of his tricks to try and blind Sunstreaker with lust.

                They’re pretty good tricks.         

                “It’ll be ok. But only if you start now,” Sideswipe says after pulling away. He licks the point of Sunstreaker’s chin and gazes up at him with a desperate expression. “Please…?”

                It’s always been hard to deny Sideswipe anything, especially when he looks at Sunstreaker like this. Plus, Sideswipe isn’t the only one who likes the thrill of flirting with danger.

                “Okay,” Sunstreaker says, a little faintly. Sideswipe squirms excitedly, making Sunstreaker see sparks.

                “Can I be on top?” Sideswipe asks as Sunstreaker’s pace starts to quicken. Sunstreaker had been close to overload before Sideswipe had said anything; the prospect of engaging his mod gets Sunstreaker even closer.

                Sunstreaker considers it. Last time, Sideswipe had been on his knees with Sunstreaker behind him. The only drawback to the position had been Sunstreaker missing Sideswipe’s expressions as he had wailed out his pleasure.

                “Yeah,” Sunstreaker replies, voice burring around the edges with static. “After it engages though, ok?”

                Sunstreaker doesn’t quite trust Sideswipe not to hurt himself; with Sunstreaker on top and better to control the initial penetration, that won’t be an issue. Sideswipe pouts for about half a second, but a particularly hard thrust quickly turns the pout into a happy moan.

                “Ok,” Sideswipe whispers, shuddering. “But get going already.”

                “I’m not a dog on command,” Sunstreaker retorts, but the words lack any real heat; he had just hit the point of no return. The protocols for engaging his mod pop up on his HUD and he accepts them. He can feel the changes take place in his spike almost immediately.

                Firming further. Thickening at the base. His transfluid tank spasms as well, prepping to empty completely. Sunstreaker briefly closes his optics, savoring the sweet ache.

                “Uh huh. Woof, woof,” Sideswipe says, voice shaking with both humor and eagerness. “Mmmm… oh, Sunny, I can feel it…”

                Sunstreaker opens his optics and stares down at his brother. Sideswipe is looking back at him with a sort of hazy awe and Sunstreaker’s thrusts become slower and deeper as his knot forms.

                It doesn’t take long for it to reach full size. Between one thrust and the next, it catches behind Sideswipe’s valve lips. Sunstreaker stills, spark whirling madly at the pleasure of a rippling, tight glove around his spike. He instinctively grinds against Sideswipe and his brother groans, hips thrusting up once before an overload washes over him.

                Sunstreaker sadly misses watching it play out over Sideswipe’s face. The clench of Sideswipe’s valve drags Sunstreaker that fraction deeper and completely locks his spike in place. His own overload begins, the first jet of transfluid spurting into the depths of Sideswipe’s valve. Sunstreaker is momentarily blinded by the streak of pleasure and his hips automatically hunch forward.

                “Ohhh, frag… oh, frag, yeah, that’s it,” he dimly hears Sideswipe moan. His brother’s fingers dig into Sunstreaker’s back and he forces his optics open to see Sideswipe biting at his lower lip.

                “Ok?” Sunstreaker manages because despite how good it feels, Sideswipe’s the one most at risk here. And he will never hurt his brother, not even for this.

                Sideswipe’s optics lazily flicker on and he gazes up at Sunstreaker adoringly. “ _So_ ok. Now? Can I get on top now?”

                Sunstreaker shudders as the next spray of transfluid leaves him in another mini overload. He nods his head, knowing there’s about a twenty to thirty second pause between each wave.

                “Yeah, just… be careful,” he cautions, leaning down to press against Sideswipe’s chest. Sunstreaker then rolls to the side, Sideswipe clinging to him. Sunstreaker settles on his back and Sideswipe shifts to a sitting position.

                He freezes halfway there, a worrying little noise slipping out from between his lips. Sunstreaker clutches at Sideswipe’s waist, gaze trying to decipher his twin’s expression.

                “Sides?”

                Sideswipe lets out a shaky ventilation. “… just need a second.”

                Sunstreaker feels everything inside his lower abdomen tighten suddenly. “I don’t really have one,” he says as his tank ripples again. Only through sheer force of will is he able to restrain the automatic urge to thrust.

                Sideswipe gasps, fingers scraping against Sunstreaker’s chestplate. Optic shutters clenching shut, he hunches forward slightly, biting his lip. Sunstreaker is pretty sure it’s not in pleasure this time.

                “We can roll back over,” Sunstreaker suggests, already moving. He’s stopped when Sideswipe’s right hand raises up and slams back down on Sunstreaker’s hood, making a dull thumping sound.

                “I’m good,” Sideswipe insists, opening his optics to glare at Sunstreaker. “Don’t you go _anywhere_. Things just… shifted. I’m ok.”

                “Are you sure?” Sunstreaker presses, staring at Sideswipe in worry. But even as he asks, he can see the lines of tension start to melt away in Sideswipe’s body. Sideswipe slowly straightens, aft settling completely against the tops of Sunstreaker’s thighs.

                Just in time too as another wave unexpectedly hits Sunstreaker and he can’t stop the tiny jerk of his pelvis. It’s not as bad with Sideswipe’s full weight on him and after Sunstreaker’s whimper has faded, his flickering sight sees Sideswipe smile down at him.

                “I’m sure,” Sideswipe purrs. He strokes Sunstreaker’s chest, thumbs flicking around the headlights as he circles them. One hand continues on down to their groins and Sideswipe slips a hand between them, fingers moving in little back and forth rubs over his anterior node. “Now you gonna give me everything you got or what?”

                Sunstreaker eventually does, Sideswipe pushing himself into three more climaxes until he’s a shaking mess, condensation dripping down his frame. Sunstreaker’s no better, his processor swimming from the excess heat his body is giving off. He’s pretty hazy at the end, barely able to focus on anything other than his thumb slipping against Sideswipe’s nub.

                Sideswipe’s leaning back, supporting his weight with shaky arms. His hands grip Sunstreaker’s knees, fingers flexing as his charge climbs higher and higher. Even with the knot as big as it is, Sideswipe’s still undulating on top of him, grinding his hips in little figure eights. He’s chasing after his final overload in single minded determination, and he finally catches it, coming with a strangled shout.

                He shudders and shakes, valve so, so tight around Sunstreaker’s spike. Sunstreaker’s transfluid tank is just about empty, the last few spurts forceful enough to almost hurt as they leave him. One or two more and he’ll be finished.

                “Help…” Sideswipe gasps, flailing a bit. They’re both a little uncoordinated, but Sunstreaker manages to grab Sideswipe’s hand and tugs him forward. Sideswipe collapses against Sunstreaker’s chest and the last of Sunstreaker’s transfluid erupts out of him with one final burst of white-hot pleasure.

                His processor goes a little blank for a bit as his body begins to wind down. He hangs onto Sideswipe’s waist, fingers more just resting there than actually gripping the plating. Sunstreaker doesn’t really have the strength for that. He doesn’t have the strength for much of anything besides lying prone, Sideswipe’s frame too-hot and too-heavy and just right on top of him.

                After some undetermined about of time (did Sunstreaker’s chronometer short out? Can that actually happen?) Sideswipe stirs. His hand slides up, over Sunstreaker’s shoulder, briefly caresses the side of Sunstreaker’s face, and then lands on top of his helm. Sideswipe gives it a little pat.

                “Good dog,” he murmurs.

 

~ End


End file.
